I finally decided to upgrade, and unfortunately I have a big problem with xorg, actually with the ati driver.
Until version 4.3 there was a "iBooksHacks" option that worked pretty well. Now it has been changed into "MacModel". I've tried all the models written in the man page with no success.
The problem is: I can get into X, but then I cannot go back to console, the computer would freeze, the monitor would display "input not supported" and I can't even get in from a different machine, I can only cut the power.
I'v tried also without the "MacModel' option, and I can still get into X but no way back.

If anyone has any idea to solve the problem it would be great, otherwise I guess I''l be obliged to switch back to 4.3.

Perhaps you can try generating a new configuration file.. i.e: X -configure.

Can you post a dmesg in [code][/code] blocks, and perhaps post /var/log/Xorg.0.log.

I have never used OpenBSD on Apple hardware nor I am planing to do that in the future but I have a few questions.

Is MAC mini PPC or i386? Secondly, I am little bit surprised to see that you advice him to run X -configure? On sparc64 let say you configure X by starting with xorg.conf file provided in /usr/X11R6/README and editing it. Are you suggesting that MAC hardware can be configured as i386 and
AMD64. What about advice to keep OS X on the small portion of the
HDD to help configuration and etc.

As I said, I have never used OpenBSD on MAC, I have never even read
carefully FAQ pages about X on MAC so I might be asking completely stupid things.

It is PPC as stated in the thread title.
In the past, if I did not use X -configure, xorg would not get things right, especially, I have to specify the HorizSync and VertRefresh.
OpenBSD 4.3 worked just fine (and so did 4.2) with the "iBooksHacks".
When I bought this macmini in 2005 (one of the first, I guess) it was to switch "from" mswindows, but then I found out I like mac osx even worst. The good is, it pushed me to learn unix. So I don't want to waste disk space for something I will never use. And as I said, things were just fine in 4.3. Actually, at the time I tried different OS: freebsd, netbsd, slackware, fedora, but openbsd overall gives less problems (or none at all), For examplel, with freebsd and slackware the fan keeps running, whereas there are no such problems with openbsd, the install is also easier with openbsd.

The entire history of OpenBSD source-code is publicly available via CVS repository, including comments for every change by the developers. If you know how you configured it in your xorg.conf file when you were running 4.3, what it did and why it was removed can be found in the xenocara CVS repository.

well, I had a look at the repository, but I'm a bit lost, I've been clicking around a lot, but don't really know how to make a clever search. I guess I might wait until the next release and in the meantime reinstall 4.3

Here's a cheat to find the appropriate log entries: Install CVSync, obtain a copy of the relatively small CVSROOT repository, then grep the Changelog* files looking for comments about the hack, which will lead you to the appropriate source.

I don't have access to my CVS repositories today, else I would just do this myself.

BTW, a search of the misc@ archives showed that the hack was in place at least as far back as 3.4 or 3.5. That would be in the XF4 repository, which has been retained for historical purposes such as these. Xenocara was put in place for the restructured Xorg 6.9, if I remember correctly.

While I don't have access to my CVS repositories, I do have access to my cvsync.conf file, which shows all the repositories I keep. If you wish to copy/paste/edit it, you'd only require the "openbsd-cvsroot" repository collection.

I'm back
Thank you guys.
Actually I just wanted to ask you if it weren't better to tell this directly to the obsd developers. I've tried all the possible combinations of MacModel: "mini", "mini-internal", "mini-external" all give access to X with no way back (while in X all works fine); all "powerbooks" options give a black screen with no way out; "ibooks" gives a black screen but allows to go back to console.
Now I have 4.4 instlled, with nothing in it, because I tried everything: fresh install of 4.4, re-installation of macos X to see if it was ofirmware related (a fresh installs resets everything), I reinstalled 4.3 and found out the old "iBookHacks" words fine. Reinstalled 4.4 and double-checked all the "mini" options, nothing works.
Here is the xorg.conf (this time with "mini" option):

Actually I just wanted to ask you if it weren't better to tell this directly to the obsd developers.

To do that, you file a report. Posting to misc@ can sometimes be helpful -- its a much bigger crowd, including some of the developers, but not all of them. misc@ is better if you want to know why or how. But for something like this, which appears to be a bug, it's best to contact the developers with a bug report.